A federal judge has upheld the historic landmark designation for the exterior and interior of the Warner Theater, dismissing claims by the building's owners that the delays in the designation process had rendered the building "immune" to efforts to protect it under the D.C. Preservation Act.

Judge Louis F. Oberdorfer's decision, handed down two weeks ago, is the most recent chapter in a five-year struggle between the D.C. Preservation League and the building's four principal owners, who have fought landmark designation for the 62-year-old theater. The four are J. Albert Weinberg, South Trimble III, Julius Goldstein and Simon E. Eichberg.

The D.C. Historic Preservation Review Board agreed to designate the Warner -- the last remaining "picture palace" in downtown Washington -- after several days of lengthy public hearings last summer, during which the owners' attorney attempted to have members of the preservation review board disqualified and evidence submitted by preservationists thrown out.

The Warner's owners never have said publicly what they would like to do with the theater and office building on the site, but have said that the building would lose $6.5 million in value if designated as a historic landmark.

In their U.S. District Court appeal, the owners asked to have the designation ruled invalid because of a procedural delay. The Joint Committee on Landmarks, which handled historic designations before the review board was established in 1983, had failed to act on the designation application for the Warner within 90 days, as required by the law.

The owners said in their appeal that they believed this delay rendered the building forever exempt from historic designation. They also claimed that the portion of the D.C. Preservation Act that applies to the interiors of historic buildings was unconstitutional because, they said, there was no public purpose to protecting historic interiors if the law did not also require them to be open to the public.

Oberdorfer ruled, however, that the delay of the landmarks committee -- which was not a D.C. agency -- was not sufficient reason to penalize the public interest by exempting the Warner from protection. Oberdorfer also upheld the constitutionality of the section of the law that allows the city to protect historic interiors, saying that public viewing was not necessary to serve a public purpose.

William W. Taylor III, the lawyer for the principal owners of the Warner, said they plan to appeal the decision.

The D.C. Court of Appeals has rescinded a recent decision that changed the interpretation of the rent control laws and barred many of the owners of condominiums from the small-landlord exemption. The appeals court now will rehear the case sometime in the next month.

Most rented condominium units generally had been considered exempt from the city's stringent rent control laws under the small-landlord exemption, until an appeals court ruling in January that said rent control applied to any condo in any building where five or more units were rented.

Before that, the real estate community and the D.C. Rental Housing Commission had interpreted the small-landlord exemption as applying to anyone who owned and rented no more than four units, no matter how many units in the building were rented.

The appeals court, however, said that was a "misreading" of the statute's language. The court said that the correct reading was that the small-landlord exemption would not apply to a rented unit if there were more than four units in a building being rented. That decision all but eliminated the small-landlord exemption for people renting out condominium units, as most of the city's large condominiums have a mixture of owner-occupants and tenants.

Under the new interpretation, condominium lawyers said, thousands of condominium tenants could be entitled to pay lower rents and collect substantial refunds from their landlords.

The D.C. City Council, reacting to concerns from condo owners, has passed emergency legislation that temporarily extends the small-landlord exemption from rent control to the owners of rental condominiums. The council also is considering a bill that would permanently correct the problem with the language of the rent control law if the court's rehearing results in an interpretation similar to the earlier decision.

American families are smaller than they used to be, but their homes are larger. They are more comfortable as well, with amenities once considered luxuries now almost commonplace. They cost more, too, of course.

The Census Bureau reports that the average American home had 5.1 rooms in 1983, the most recent statistics available, an increase from 5.0 in 1970 and 4.9 in 1960. The median price of homes -- half cost more, half less -- being sold climbed to $75,200 in 1985. That's up from $20,100 in 1968, when the National Association of Realtors started keeping track.

Televisions are the most popular appliance in American homes. The A. C. Nielsen Co. estimated a few years ago that 98 percent of all U.S. homes had at least one television set, and the percentage probably has climbed since then. The Census Bureau, in 1982, found that color sets were in 84.8 percent of homes.

In 1982, the Energy Department said virtually every home in America had at least one refrigerator. Other popular appliances are: clothes washers, in 71.4 percent of U.S. homes; clothes dryers, 59.8 percent; electric ranges, 53.3 percent; electric ovens, 51.9 percent; gas water heaters, 51.1 percent; gas ranges, 46.6 percent; gas ovens, 41.7 percent; freezers, 37.0 percent.

Also: dishwashers, 36.1 percent; electric water heaters, 30.4 percent; window or ceiling fans, 28.0 percent; microwave ovens, 20.7 percent; humidifiers, 13.5 percent; outdoor gas grills, 11.2 percent; portable electric heaters, 9.2 percent; dehumidifiers, 9.0 percent; whole house cooling fans, 7.8 percent.

IN THE BUSINESS . . . Virginia home sales were up 24.5 percent in February, with 6,589 sold in the state last month and 5,292 a year earlier, according to the Virginia Association of Realtors . . . Cathie Gill, president of her own firm, received the first-place award from the Million Dollar Residential Sales and Listing Club for producing more than $22 million worth of sales and listings last year . . . Maryland Land Title Association, a group for land title professionals, has elected Joseph G. Blume Jr. of SAFECO Title Insurance Corp. as president . . . Long & Foster said it sold $359 million worth of real estate in February, up 52 percent over the same month last year . . . Curtis Homes, a suburban Maryland builder, has been renamed Preference Homes in the wake of Charles W. Bowie's purchase of the firm last year . . . Washington Homes has started construction on the $5.7 million 65-unit Quailwood town-house development near LaPlata . . . Maryland Corporate Center has started construction on the second phase of a 28-acre office park that is planned to total 600,000 square feet near the Goddard Space Flight Center in Prince George's County . . . Ground was broken this week for Hampden Square, a 221,300-square-foot, $30 million commercial office, retail and residential complex in Bethesda's business district . . . Capital Homes reports more than $42 million in new home and land sales during 1985 . . . Atlanta University and Morehouse College in Atlanta have announced the creation of the country's first endowed professorship of commercial and residential real estate at historically black schools . . . Oxford Development Corp. is forming another subsidiary, Oxford National Management Corp., to manage properties its acquires from third parties . . . George Hyman Co. has won the contract to build the new Canadian Embassy along Pennsylvania Avenue NW near the Capitol . . . Pettit & Griffin Inc. has won Montgomery County approval for construction of a 93,360-square-foot shopping center at Laytonsville Road and Flower Hill Way in Gaithersburg . . . Walker and Co. has started construction on the 115,000-square-foot Parkridge Three Building in Reston . . . Miss Utility, which provides information on the location of utility lines and pipes prior to the start of any construction work, has a new toll-free number: 1-800-257-7777.

PERSONNEL FILE . . . James R. Miller Jr. has been promoted to senior vice president of Weaver Bros. Inc. . . . Smithy Braedon has promoted five persons to vice president: William T. Comerford Jr., Gary A. Faigen, Barbara Gravett, Robert D. Priest and Vincent W. Chiarello . . . Allan T. Walsh has joined Artery Capital Group, involved in the purchase and syndication of income-producing real estate, as a vice president for acquisitions.